This invention relates generally to semiconductor fabrication, and more particularly, to inhibiting particle contamination of a surface, such as a surface of a reticle, a mask, a mask blank, a wafer, a substrate, a glass plate, etc.
The electronics industry continues to rely on advances in semiconductor technology to realize ever higher-functioning devices in more compact areas. For many applications, realizing higher-function devices requires integrating a larger and larger number of electronic devices into a single wafer. As the number of electronic devices per area of wafer increases, the manufacturing processes become more intricate.
One of the process steps encountered in the fabrication of integrated circuits and other semiconductor devices is photolithography. Generally stated, photolithography includes selectively exposing a specially-prepared wafer surface to a source of radiation using a patterned template to create an etched surface layer. Typically, the patterned template is a reticle, which is a flat, glass plate that contains the patterns to be reproduced on the wafer.
The industry trend towards the production of integrated circuits that are smaller and/or with higher logic density necessitates ever smaller line widths. The resolution with which a pattern can be reproduced on the wafer surface depends, in part, on the wavelength of ultraviolet light used to project the pattern onto the surface of the photoresist-coated wafer. State-of-art photolithography tools use deep, ultraviolet light, with wavelengths of 193 nm, which allow minimum feature sizes on the order of 100 nm. Tools currently being developed use 157 nm extreme ultraviolet (EUV) light to permit resolution of features at sizes below 70 nm.
Extreme ultraviolet lithography (EUVL) is a significant departure from the deep, ultraviolet lithography currently in use today. All matter absorbs EUV radiation, and hence, EUV lithography takes place in a vacuum. The optical elements, including the photo-mask, make use of defect-free multi-layers, which act to reflect light by means of interlayer interference. With EUV, reflection from the patterned surface is used as opposed to transmission through the reticle characteristic of deep, ultraviolet light photolithography. The reflective photo-mask (reticle) employed in EUV photolithography is susceptible to contamination and damage to a greater degree than reticles used in conventional photolithography. This imposes heightened requirements on reticle handling destined for EUV photolithography use. For example, any particle contamination of the surface of the reticle could compromise the reticle to a degree sufficient to seriously affect the end product obtained from the use of such a reticle during processing. The problem is particularly significant in, for example, a transfer chamber, such as a load-lock structure, where changing pressure between atmospheric and vacuum creates turbulence within the chamber, and thus increased likelihood of contamination.